The present invention relates to a fuel injection valve used in internal combustion engines to inject a swirling fuel to enable achieving an improvement in atomizing performance.
A fuel injection valve described in JP-A-2003-336562 is known as prior art, in which a swirling flow is made use of to accelerate atomization of a fuel injected from a plurality of fuel injection ports.
In this fuel injection valve, a lateral passage in communication with a downstream end of a valve seat and a swirl chamber into which a downstream end of the lateral passage is opened tangentially are formed between a valve seat member, to a front end surface of which a downstream end of the valve seat cooperating with a valve body is opened, and an injector plate joined to the front end surface of the valve seat member, and a fuel injection port, from which a fuel given swirl in the swirl chamber is injected is formed in the injection plate, and the fuel injection port is arranged offset a predetermined distance toward an upstream end of the lateral passage from a center of the swirl chamber.
Also, in this fuel injection valve, an inner peripheral surface of the swirl chamber is decreased in radius of curvature toward a downstream side from an upstream side in a direction along the inner peripheral surface of the swirl chamber. That is, the curvature is increased toward the downstream side from the upstream side in the direction along the inner peripheral surface of the swirl chamber. Also, the inner peripheral surface of the swirl chamber is formed along an involute curve having a basic circle in the swirl chamber.
Such construction enables effectively accelerating atomization of a fuel from respective fuel injection ports.
In order to inject a swirling fuel, which is symmetric (uniform) in swirl intensity in a circumferential direction, from a fuel injection port, it is necessary to contrive a flow passage configuration including the shape of a swirl chamber and a lateral passage (swirl passage) in order to make a swirling flow symmetrical at an outlet of the fuel injection port.
In the prior art described in JP-A-2003-336562, one (a side wall connected to an upstream end of an inner peripheral surface of a swirl chamber in a fuel swirling direction) of side walls, which define a lateral passage, is connected tangentially to the inner peripheral surface of the swirl chamber and the other (a side wall connected to a downstream end of the inner peripheral surface of the swirl chamber in the fuel swirling direction) of the side walls is provided in a manner to intersect the inner peripheral surface of the swirl chamber. Therefore, a connection of both walls, on which the other of the side walls and the inner peripheral surface of the swirl chamber intersect each other, is shaped to be sharp at the point like a knife edge.
With such connection, when the side wall of the lateral passage or the inner peripheral surface of the swirl chamber is minutely dislocated, the connection of both walls is liable to be dislocated. Such dislocation of the connection is responsible for generation of steep drift toward a fuel injection port, so that it is possible that a swirling flow is damaged in symmetric property (uniformity).